This research project involves studies preparatory to the eventual clinicial application of biventricular assist and total artificial heart (TAH). Having significant experience in TAH research and well aware of the state-of-the-art, our group proposes to identify, clarify and solve problems associated with practical clinical total heart assist and replacement including physiological, material, and surgical procedural aspects. The objectives are: 1) to separate and clarify the transient versus the permanent physiological changes in the recipient, determine cuases, and find solutions, 2) investigate material problems such as pannus formation at interfaces, calcification of pump surfaces, and control of infection (endocarditis), 3) evaluate adapting a pair of existing left ventricular assist pumps to biventricular assist or replacement, 4) study the feasibility of TAH removal and implantation in the same recipient simulating the intermediary (up to six months) clinical TAH. These preclinical experiments will be of 4 to 8 months duration in calves. The experiments will be graded in complexity with each series serving as controls for those following. Approximately twenty experiments, including both total replacement and biventricular bypass, will be conducted. The design of the pumps, materials of construction and experimental protocols have been established on several prior and existing research contracts and grants.